Need help with RF Module and EMI

Questions, comments, suggestions on RFToy

Need help with RF Module and EMI

Postby hyuna » Mon Dec 12, 2016 2:54 am

I am using a RF module(RXM-433-LR) in a design with several switching regulators. My implementation is as follows:
When the switching regulators are on (and heavily loaded at approximately 500-700 mA) the RF module is swamped and my range is reduced significantly. When unloaded, things are just fine. I can watch the RSSI pin jump when these loads come up.

The datasheet for the module says that it is very susceptible to conducted emissions which is the reason for R24, C49 and C82. Probing the input, things look very clean.

My switching regulator layout is as tight as I can imagine (you might see things differently). The board is 4 layers with an internal power and ground plane. The inductors I have chosen are shielded and I am using Laird EMI shields around each switcher as well.
I am looking for any suggestions to reduce conducted and radiated emissions. I realize I can change the antenna and it's location to increase the signal with respect to the noise but at the moment I am interested in simply reducing the noise (for a variety of reasons). Any thoughts?
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